EP0005708A1 - Gel filtration column - Google Patents

Abstract

In the case of a gel filtration column for separation processes on an industrial scale, the problem of compressing the gel filling (4), which leads to a reduction in throughput and unsharp separation, is solved according to the invention in that the gel chamber (2) filled with a filter gel is separated by partition walls arranged parallel to the column wall (1) ( 3) is divided, which are shorter than the gel chamber (2) and preferably consist of concentric tubes (3) at intervals of 20 to 120, preferably 40 to 80 mm.

Description

The invention relates to an improved gel filtration column and an improved gel filtration process using the column.

On the laboratory scale, gel filtration is a simple and safe method to remove relatively small amounts of aqueous solutions containing high molecular weight, e.g. Proteins, and low molecular weight e.g. Salts, included, break down into their components. If the solution to be separated and the eluent subsequently used are introduced uniformly, generally limited fractions of the constituents contained in the mixture of substances introduced can be eluted with decreasing molecular weight.

The transfer of the process to the industrial scale, in which kilogram quantities of substance mixtures are separated in the form of aqueous solutions, often presents considerable difficulties. The flow rate, which is dependent on the packing density of the gel column and on the viscosity and the batch quantity of the solution to be processed, decreases with increasing column cross section as a result of increasing compression of the gel filling. At the same time, the separation behavior changes. Since a uniform flow of liquid is essential to achieve a sharp and reproducible fractionation of the mixture, both the solution to be separated as well as the eluent are mostly pumped into the column with a constant delivery volume. When the liquid permeability of the gel filling drops below the delivery volume of the pump, a liquid back pressure builds up in the inlet chamber of the column, which compresses the gel even more and further reduces the permeability. At this stage, the process must be interrupted and the gel filling returned to its original state in a time-consuming process.

Such malfunctions can be avoided or at least delayed if the column filling is divided into a large number of flat layers. However, the sharpness of the fractionation suffers from this. In addition, the required equipment becomes larger and more expensive, and the loading with fresh gel and the removal of the used gel become more complicated. This applies even more if you use a large number of thin columns in parallel instead of a column with a large cross-section.

Further measures to reduce these disadvantages are the dilution of the solution to be treated in order to reduce its viscosity, and the reduction of the batch quantity and flow rate. All of these measures reduce the overall performance of the column.

A chromatography column is known from US Pat. No. 3,856,681, which consists of a multiplicity of thin layers of the chromatographic separation material which run parallel to the column axis. The individual layers are separated from each other by inert plastic or metal foils. The height of the column is determined by the length of the separating foils, ie the column filling closes at the top and bottom of the column with the top edge of the separating film. Apart from the cumbersome way of manufacturing the column, in which a film band coated with the chromatographic filler material is wound into a column, it is difficult to ensure a uniform gel filling in all vertical segments of the column. This leads to uneven separation conditions in the vertical column segments, with the consequence of a correspondingly reduced selectivity.

The object was to create a gel filtration column for operation on an industrial scale, whose liquid permeability does not decrease even during continuous operation and which allows a separation behavior corresponding to the laboratory scale with the same performance per unit area. The column should continue to be simple in construction and easy to fill and empty. This object is achieved by the gel filtration column characterized in the claims.

The partition walls arranged in the gel chamber of the column effectively prevent the gel filling from being compressed. Columns of any size and height can be created. A larger effective column height can also be achieved with little effort by connecting two or more columns in series. The usual dextran gels, polyacrylic gels or other gels are used as filling.

• Figur 1 zeigt einen senkrechten Schnitt durch die Mittelebene der Kolonne.
• Figur 2 stellt einen Querschnitt in der Ebene A-B der in Figur 1 gezeigten Kolonne dar.
• Figur 3 zeigt einen gleichartigen Schnitt bei etwas veränderter Bauart der Zwischenwände.

Appropriate embodiments of the gel filtration columns according to the invention are shown in FIGS. 1 to 3.

• Figure 1 shows a vertical section through the central plane of the column.
• FIG. 2 shows a cross section in the plane AB of the column shown in FIG. 1.
• Figure 3 shows a similar section with a slightly different design of the partition walls.

According to the invention, the partition walls (3) are shorter than the gel chamber (2), so that the gel filling (4) projects above and below the end of the partition walls. A difference in length of 5 to 20%, preferably about 10%, of the gel chamber height is usually the most advantageous. This creates matching process conditions in all vertical column segments (5), which in turn ensures uniform separation in each segment and thus a high degree of selectivity.

In order to make the conditions in all vertical segments as uniform as possible, the partitions are arranged one below the other and from the column wall (1) at the most uniform intervals (a). The required distances depend somewhat on the size of the gel particles; fine particles require small distances, coarser particles allow larger distances. The distances are generally 20 to 120 mm, preferably 40 to 80 mm. It is sufficient to keep these distances between the walls, while no further subdivision is necessary along the walls.

The arrangement of the partition walls depends on the outer shape of the column wall (1) and the suitability for production. Concentric tubes (3) or parallel stacked plates (6) are as simple as they are useful. The partitions are connected to one another by brackets (7), which can also be designed as continuous partitions, but can also consist of individual narrow spacers. The gel chamber (2) is expediently delimited from the inlet and outlet chambers (11, 12) with sieve trays (9, 10), the openings in the sieve trays being smaller than the diameter of the swollen gel particles. The inlet and outlet lines (13, 14) are connected to the inlet and outlet chambers (11, 12).

The bottom (16) and lid (15) of the column, like the sieve trays (9, 10), are detachably arranged in order to facilitate the loading and emptying of the gel filling. The partitions (3) connected to one another to form a fixed structural unit with the holders (7) can also be removed as a whole. The ends of the brackets (7) can e.g. rest on brackets (8) on the column wall (1).

The gel material is generally filled in as dry granules and swells somewhat when filled with water or the aqueous liquid to be used for operation. The amount of gel material filled in is preferably such that its swelling volume, which it takes up when the swelling is unobstructed in space, would take up slightly more than the free gel chamber volume. In the swollen state, the gel filling is therefore under a slight pressure, which counteracts the tendency to compact the filling. It is important to have a uniform swelling pressure in all vertical segments, because only then will the separation effect be the same in all segments and the separation efficiency of the entire column be high. The uniform swelling is ensured by the fact that the partition walls are shorter than the gel chamber. Small irregularities in the amounts of gel that are present in the individual segments compensate themselves automatically if the gel filling swells over the upper edge of the partition walls in the course of the swelling process.

In the operating state, the column is generally completely filled with liquid. The direction of flow during operation is arbitrary.

The gel filtration column according to the invention, like corresponding known devices, is operated in two steps. In the feed step, the aqueous solution containing a mixture of high and low molecular weight components is run into the column while at the same time withdrawing an equal amount of the original liquid filling. The elution is then carried out, the highest molecular components of the solution being eluted first. When the lowest molecular weight components are fully eluted, a new work cycle consisting of a task and an elution step can be started.

In order to counteract gradual compression over many working cycles and to maintain unchanged operating conditions indefinitely, it is advisable to reverse the flow direction after each working cycle, since the column delivers the same results in every flow direction.

Claims (4)

1. gel filtration column with at least one gel chamber filled with a filter gel, which is divided by partition walls arranged parallel to the column wall,
characterized in that the partitions are shorter than the gel chamber. 2. Gel filtration column according to claim 1, characterized in that the partitions with one another and from the column wall have distances of 20 to 120, preferably 40 to 80 mm. 3. Gel filtration column according to claims 1 and 2, characterized in that the partition walls consist of concentric tubes. 4. gel filtration column according to claims 1 to 3, characterized in that the swelling volume of the gel enclosed in the gel chamber is greater than the free volume of the gel chamber.

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